Trevor P. Scott

Trends in the surgical treatment of lumbar spine disease in the United States

BACKGROUND CONTEXT There is a lack of agreement among spine surgeons as to the best surgical treatment modality for many degenerative lumbar diseases. Although there are many studies examining trends in spinal surgery, specific studies reporting the variations in surgical treatment in the United States for these diseases are lacking. PURPOSE The aim of this study was to analyze trends in lumbar spinal fusion methods for common lumbar pathologies in the United States. STUDY DESIGN/SETTING National insurance database review: 2004-2009. PATIENT SAMPLE Data is taken from United Healthcare and represents more than 25 million patients. OUTCOME MEASURES No outcomes were measured in this study. METHODS Using a private insurance database, we identified patients who underwent one of five types of instrumented single-level lumbar spinal fusion for the 10 most common primary diagnoses. Surgery rates were reviewed from 2004 to 2009 and were stratified according to patient age, patient gender, and region in the United States. Poisson regression analysis was performed to determine regional and demographic differences in treatment modality. The authors received no funds in support of this work. RESULTS A total of 23,986 patients met our search criteria. Of the five fusion types, posterior lumbar interbody fusion (PLIF) with posterolateral fusion (PLF) was the most common (45%), followed by PLF (19%), anterior lumbar interbody fusion (ALIF, 16%), PLIF (10%), and ALIF with PLF (9%). There was a significant increase in PLIF with PLF (p<.0001), PLIF (p<.0001), PLF (p=.012), ALIF (p<.0001), and ALIF with PLF (p<.0001) from 2004 to 2009. After controlling for gender, there were significant differences between regions for all fusion types (p<.0001). The likelihood of a posterior fusion increased with age. Anterior fusions were more common in the 30- to 49-year-old age range than in patents older than 50. For patients in age groups older than 30, there was an increased number who underwent a circumferential fusion or an ALIF (p<.022). Fusion types were significantly different between genders (p<.026). Both genders had an overall increase in the number of fusions (p<.001) over the time period studied. CONCLUSIONS There are large differences in the United States for surgical treatment methods for lumbar spine pathology. These differences are likely multifactorial, with both patient and surgeon traits playing a role. Illustrating these differences will hopefully lead to outcomes research to determine the indications, efficacy, and appropriateness of these surgical methods, an important step on the path toward standardization of care.

Trends and Demographics in Anterior Cruciate Ligament Reconstruction in the United States.

The purpose of this study was to identify the trends and demographics of patients undergoing arthroscopic anterior cruciate ligament (ACL) reconstruction in the United States. Patients who underwent arthroscopic ACL reconstruction between 2004 and 2009 were identified by searching Current Procedural Terminology codes in the PearlDiver Patient Record Database (PearlDiver Technologies, Fort Wayne, IN). The year of procedure, age, gender, and region of the United States were recorded for each patient. Associated meniscal procedures and the absence or presence of a femoral nerve block were also recorded. The incidence of ACL reconstruction significantly increased over the study period, from 40.9 cases per 10,000 patients in 2004 to 47.8 in 2009 (p < 0.001). Of these cases, 92.8% were associated with either meniscectomy or meniscal repair. ACL reconstruction was performed most commonly in patients aged 10 to 29 years (p < 0.001). A significant male predominance was observed with an incidence ratio of male-to-female of 2.03 (p < 0.001). The frequency of females undergoing ACL reconstruction as a proportion of the total number of annual cases increased from 2,295 in 2004 to 3,476 in 2009 (p = 0.0031). A significant increase in the annual proportion of ACL reconstruction performed under femoral nerve block was also observed, from 2.0% in 2004 to 8.3% in 2009 (p < 0.001). The greatest incidence of ACL reconstruction occurred in the Western region of the United States. An increase in the rate of arthroscopic ACL reconstruction was observed between 2004 and 2009 and 92.8% of the ACL reconstructions were associated with a meniscal procedure. The majority of cases were performed in patients aged 10 to 29 years, with a male predominance. Increases were observed in the number of female cases and proportion performed under a femoral nerve block. The Western region of the United States was found to have a higher incidence of ACL reconstruction.

Effect of cervical kyphotic deformity type on the motion characteristics and dynamic spinal cord compression.

Study Design. Retrospective analysis of kinematic magnetic resonance images. Objective. To provide baseline data on the segmental angular and translational motion of the degenerated cervical spine by subtype of kyphotic cervical deformity and to elucidate the relationship between motion and degree of spinal cord compression. Summary of Background Data. Kyphotic deformities of the cervical spine are relatively common and are classified as either global or focal. Nevertheless, the effects of kyphotic subtype on cervical segmental motion and degree of spinal cord compression are unknown. Methods. A total of 1171 symptomatic patients (618 females, 553 males) underwent cervical kinematic magnetic resonance imaging in the neutral, flexion, and extension positions. Cervical spines demonstrating kyphosis were included and classified into 3 groups: (1) “global kyphotic deformity” (C-type) (n = 54); (2) “sigmoid deformity” (S-type) with kyphotic upper and lordotic lower cervical segments (n = 29); and (3) “reverse sigmoid deformity” (R-type) with lordotic upper and kyphotic lower cervical segments (n = 39). Translational motion, angular motion, and degree of spinal cord compression were evaluated for each cervical level along with the changes associated with flexion and extension. Results. In the C- and R-types, angular motion with extension was increased in the upper cervical spine, where there was kyphosis; when compared with the S-type, in which there was lordosis in the upper segments. The results were opposite for flexion angular motion. R-type displayed more translational motion at C3–C4 and C5–C6. Degree of static spinal cord compression of R-type was higher than the others at C3–C4. The dynamic spinal cord compression increased in extension more than flexion in all subtypes. Conclusion. Cervical spine studies that aim to investigate kyphotic deformities should make efforts to discern the different subtypes of kyphotic deformities to more accurately characterize and study the effects that the sagittal alignment has on the kinematics of the spine and the degree of spinal cord compression. Level of Evidence: 3

Risk factors for missed dynamic canal stenosis in the cervical spine.

Study Design. Retrospective analysis of kinematic magnetic resonance (MR) images. Objective. To elucidate the distribution and risk factors associated with missed dynamic stenosis in cervical spine. Summary of Background Data. Motion of the cervical spine is widely accepted to be associated with cervical spondylotic myelopathy; however, the distribution and the risk factors for dynamic spinal stenosis are not well understood. Methods. A total of 435 symptomatic patients (2610 cervical segments) obtained upright kinematic MR images in neutral, flexion, and extension postures. Spinal cord compression (SCC), spondylolisthesis, disc bulging, angular motion, translational motion, disc degeneration grade, Modic changes, segmental alignment, and developmental stenosis were all evaluated. Cervical segments C2–C3 to C7–T1 were divided into 2 groups, determined by the presence of SCC. After excluding segments with SCC in the neutral position, a multivariate logistic regression model was used to evaluate for associated risk factors of SCC in flexion and extension that were not present in the neutral position. Results. SCC in neutral position was observed in 5.3% (139/2610) of segments. After excluding these segments, missed dynamic stenosis was found in 8.3% (204/2471) of segments in extension and 1.6% (40/2471) in flexion. Missed dynamic stenosis in both extension and flexion was most frequent at C5–C6. Multivariate logistic regression analysis for dynamic stenosis in extension revealed that disc bulge greater than 2.4 mm, angular motion greater than 4.8°, moderate and severe disc degeneration, segmental kyphosis, and developmental stenosis were significant risk factors. In flexion, significant risk factors were a disc bulge of 1.9 mm or greater, moderate to severe disc degeneration, and segmental kyphosis. Conclusion. Dynamic cord compression was most common at the C5–C6 segment. Cervical segments with greater disc bulge, more severe disc degeneration, greater angular motion, segmental kyphosis, and developmental stenosis may be at risk for missed dynamic stenosis. Level of Evidence: 2

Growth-Factor Nanocapsules That Enable Tunable Controlled Release for Bone Regeneration.

Growth factors are of great potential in regenerative medicine. However, their clinical applications are largely limited by the short in vivo half-lives and the narrow therapeutic window. Thus, a robust controlled release system remains an unmet medical need for growth-factor-based therapies. In this research, a nanoscale controlled release system (degradable protein nanocapsule) is established via in situ polymerization on growth factor. The release rate can be finely tuned by engineering the surface polymer composition. Improved therapeutic outcomes can be achieved with growth factor nanocapsules, as illustrated in spinal cord fusion mediated by bone morphogenetic protein-2 nanocapsules.

Kinematic analysis of diseased and adjacent segments in degenerative lumbar spondylolisthesis

BACKGROUND CONTEXT Degenerative spondylolisthesis is a common pathologic condition that leads to lumbar instability and significant clinical symptoms. The effect of this pathology on adjacent lumbar motion segments, however, has not yet been studied. PURPOSE To characterize the motion characteristics of lumbar degenerative spondylolisthesis at both the diseased and adjacent levels in patients with low-grade, single-level lumbar degenerative spondylolisthesis using kinetic magnetic resonance imaging (kMRI). STUDY DESIGN Retrospective study of patient kMRIs. PATIENT SAMPLE One-hundred twelve patient MRIs with low-grade, single-level lumbar spondylolisthesis were included. OUTCOME MEASURES Angular and translational motion. METHODS This study compared 112 patients diagnosed with low-grade (Grade 1 or 2), single-level lumbar degenerative spondylolisthesis at L3-L4, L4-L5, or L5-S1 with 296 control patients without spondylolisthesis. Angular and translational motion were measured using patient kMRIs. The level of slip was graded according to the Meyerding classification system, and disc degeneration was classified according to the Pfirrmann system. Instability was defined as translational motion greater than 4 mm. RESULTS Lumbar hypomobility was often present regardless of the level of degenerative spondylolisthesis. A slip at L3-L4 resulted in the largest decrease in lumbar range of motion. Instability at the diseased level was most common at L3-L4 (36%), followed by L5-S1 (31%) and L4-L5 (30%). Instability at the adjacent segments was most frequent at L4-L5 (49%), followed by L5-S1 (34%) and L3-L4 (23%). Patients with stable spondylolisthesis generally had decreased angular motion at all lumbar levels. Translational motion at the diseased level was consistently increased. Disc degeneration was significantly greater at the level of slip for the L3-L4 and L4-L5 spondylolisthesis groups and equal to the control group in the L5-S1 group. There was no significant difference in disc degeneration at adjacent segments in L3-L4 and L4-L5 degenerative spondylolisthesis patients, but there was a significant decrease with an L5-S1 slip. CONCLUSIONS There were a similar percentage of patients in each degenerative spondylolisthesis group with lumbar instability. Angular motion decreased at the diseased level with L3-L4 and L5-S1 spondylolisthesis, but increased with L4-L5 spondylolisthesis. Translational motion, however, increased at the diseased level in all three groups. There was compensatory hypermobility at adjacent levels in patients with unstable spondylolisthesis at L3-L4 and L4-L5, but not at L5-S1.

Dynamic changes of the ligamentum flavum in the cervical spine assessed with kinetic magnetic resonance imaging.

The purpose of this article is to quantify changes in thickness of the ligamentum flavum (LF) associated with motion of the cervical spine and to compare the thickness of the LF at each cervical level using kinetic magnetic resonance imaging (kMRI). Two hundred fifty-seven symptomatic patients (129 men; 128 women) underwent kMRI in neutral, flexion, and extension positions. Midsagittal images were digitally marked and electronically analyzed by spine surgeons. Thickness of LF in the cervical region from C2–3 to C7–T1 was measured in all three positions. LF at C7–T1 was significantly thicker than C2–3 to C6–7 in neutral, flexion, and extension positions (p < 0.05). LF was significantly thicker in extension than in flexion at C3–4 to C6–7. LF thickness increases with extension and decreases with flexion. LF is uniquely thick at C6–7 and at C7–T1 in the extension position, which may predispose these levels to cord compression syndromes and associated neuropathies.

Comparison of a novel oxysterol molecule and rhBMP2 fusion rates in a rabbit posterolateral lumbar spine model

BACKGROUND CONTEXT The nonunion rate after lumbar spinal fusion is as high as 25%. Recombinant human bone morphogenetic protein 2 (rhBMP2) has been used as a biological adjunct to promote bony fusion. However, recently there have been concerns about BMP2. Oxysterol 133 (Oxy133) has been shown to promote excellent fusion rates in rodent lumbar spine models and offers a potential alternative to rhBMP2. PURPOSE The purpose of this study was to compare the fusion rate of rhBMP2 and Oxy133 in a randomized controlled trial using a posterolateral lumbar rabbit spinal fusion model. STUDY DESIGN This was a randomized control animal study. METHODS Twenty-four male adult white New Zealand rabbits (3-3.5 kg) underwent bilateral posterolateral lumbar spinal fusion at L4-L5. Rabbits were divided into four groups: control (A), 30-μg rhBMP2 (B), 20-mg Oxy133 (C), and 60-mg Oxy133 (D). At 4 weeks, fusion was evaluated by fluoroscopy, and at 8 weeks, the rabbits were sacrificed and fusion was evaluated radiographically, by manual palpation, and with microcomputed tomography. RESULTS Fusion rates by radiographic analysis at 8 weeks were Group A, 40.0%; Group B, 91.7%; Group C, 91.7%; and Group D, 100%. Evaluation of fusion masses by manual palpation of excised spines after sacrifice showed the following fusion rates: Group A, 0%; Group B, 83.3%; Group C, 83.3%; and Group D, 90%. Microcomputed tomography scanning confirmed these findings. CONCLUSIONS These findings in a rabbit model demonstrate that both 20- and 60-mg Oxy133 doses promote fusion that is equivalent to fusion induced by 30-μg rhBMP2 and significantly greater than the control group. The present findings confirm that Oxy133 is a promising candidate for therapeutic development as an alternative to rhBMP2 to promote spinal fusion.

The Compensatory Relationship of Upper and Subaxial Cervical Motion in the Presence of Cervical Spondylosis.

Study Design:This study was an in vivo kinematic magnetic resonance imaging analysis of cervical spinal motion in human subjects. Objective:The objective of the study was to identify associations between disk degeneration in the subaxial cervical spine and upper cervical spinal motion in patients with general age-related cervical spondylosis. Summary of Background Data:The kinematic relationship between the occipital-atlantoaxial complex and subaxial cervical spine in patients with cervical spondylosis and decreased cervical motion is not well understood. Methods:A total of 446 symptomatic patients who had neck pain with and without neurogenic symptoms were included in this study. Kinematic magnetic resonance imaging was performed with dynamic motion of the cervical spine in upright, weight-bearing neutral, flexion, and extension positions. Intervertebral disk degeneration for each segment from C2–3 to C7–T1 and sagittal angular motion between flexion and extension for each segment from Oc–C1 to C7–T1 was evaluated. Depending on the amount of sagittal subaxial angular motion, the patients were classified into 3 groups by sagittal angular motion using cutoff points based on tertile (<36-degree group: 149 cases; 36–47-degree group: 148 cases; and >47-degree group: 149 cases). Results:A significant correlation was found between subaxial angular motion and intervertebral disk degeneration, indicating that the subaxial motion decreases according to the degree of disk degeneration. Mean angular motion of the occipital-atlantoaxial complex, especially of Oc–C1, was significantly higher in the <36-degree and 36–47-degree group than in the >47-degree group, whereas no significant difference was found at C1–C2. Conclusions:Our study demonstrates that decreased subaxial cervical spinal motion is associated with intervertebral disk degeneration in a symptomatic population. This decrease in mobility at the subaxial cervical spine is compensated for by an increase in angular mobility of the upper cervical spine at the occipital-atlantoaxial complex, especially at Oc–C1.

When Is It Safe to Return to Driving After Spinal Surgery

Study Design Prospective study. Objective Surgeons’ recommendations for a safe return to driving following cervical and lumbar surgery vary and are based on empirical data. Driver reaction time (DRT) is an objective measure of the ability to drive safely. There are limited data about the effect of cervical and lumbar surgery on DRT. The purpose of our study was to use the DRT to determine when the patients undergoing a spinal surgery may safely return to driving. Methods We tested 37 patients’ DRT using computer software. Twenty-three patients (mean 50.5 ± 17.7 years) received lumbar surgery, and 14 patients had cervical surgery (mean 56.7 ± 10.9 years). Patients were compared with 14 healthy male controls (mean 32 ± 5.19 years). The patients having cervical surgery were subdivided into the anterior versus posterior approach and myelopathic versus nonmyelopathic groups. Patients having lumbar spinal surgery were subdivided by decompression versus fusion with or without decompression and single-level versus multilevel surgery. The patients were tested preoperatively and at 2 to 3, 6, and 12 weeks following the surgery. The use of opioids was noted. Results Overall, the patients having cervical and lumbar surgery showed no significant differences between pre- and postoperative DRT (cervical p = 0.49, lumbar p = 0.196). Only the patients having single-level procedures had a significant improvement from a preoperative DRT of 0.951 seconds (standard deviation 0.255) to 0.794 seconds (standard deviation 0.152) at 2 to 3 weeks (p = 0.012). None of the other subgroups had a difference in the DRT. Conclusions Based on these findings, it may be acceptable to allow patients having a single-level lumbar fusion who are not taking opioids to return to driving as early as 2 weeks following the spinal surgery.